High-energy magnon dispersion in the half-filled Hubbard model: A comparison with La$_2$CuO$_4$

TL;DR

This study compares magnon dispersion in the 2D Hubbard model and phonon-coupled Heisenberg model, finding that intermediate U/t values in the Hubbard model match experimental data for La2CuO4, unlike the phonon-coupled model.

Contribution

The paper demonstrates that the Hubbard model with intermediate U/t values accurately reproduces experimental magnon dispersion in La2CuO4, highlighting the importance of charge fluctuations.

Findings

Hubbard model with U/t<8 matches experimental magnon dispersion.

Heisenberg model with phonons does not reproduce experimental results.

Charge fluctuations are significant in cuprate magnetic properties.

Abstract

We use quantum Monte Carlo methods and single-mode approximation to study the magnon dispersion in the 2D half-filled Hubbard and phonon-coupled Heisenberg models. We find that in the Hubbard model with $U/t< 8$, high-energy magnon dispersion is similar to those observed in inelastic neutron scattering experiments in ${La}_2{CuO}_4$. On the other hand, our studies of a 2D Heisenberg model coupled to dynamic optical bond phonons, fails to reproduce the experimental dispersion. These results can be interpreted as evidence for intermediate $U/t$ and charge fluctuations in the cuprate materials.